How is elevation calculated in psi?

The calculation of elevation in psi typically accounts for the pressure changes caused by the height of a structure. Each floor of elevation represents a change in pressure due to the weight of the water and the gravitational force acting on it. For every floor above ground, it's common to receive a pressure increase, often quantified as around 5 psi per floor.

In scenarios where there are floors below grade, the pressure might decrease instead of increase. Therefore, the response that indicates adding 5 psi for each floor of elevation while also considering a subtraction for floors below grade effectively captures the complexity of pressure changes in relation to elevation. This approach acknowledges that water pressure increases with elevation, while simultaneously recognizing that deeper levels can affect pressure negatively.

Understanding this calculation is crucial for firefighting operations, as it directly impacts the ability to deliver adequate water pressure to fight fires in multi-story buildings.